Orbital elements of barium stars formed through a wind accretion scenario

Taking the total angular momentum conservation in place of the tangential momentum conservation, and considering the square and higher power terms of orbital eccentricity e, the changes of orbital elements of binaries are recalculated for wind accretion scenario. These new equations of orbital elements are used to calculate the properties of barium stars. Our results show that, during the evolution of a binary system, the system widens as it loses mass, and the orbital period increases, while orbital eccentricity remains nearly constant, which can quantitatively explain the observed (e,logP ) properties of normal G, K giants and those of barium stars. The results reflect the evolution from G, K giant binaries to barium binaries, namely, the orbits of barium stars have been modified by the mass-transfer process responsible for their chemical peculiarities, whereas most of the G, K giant binaries are probably pre-mass transfer binaries. Moreover, the results showed that the barium stars with longer orbital period P>1600 days may be formed by accreting part of the ejecta from the intrinsic AGB stars through wind accretion, while those with shorter orbital period may be formed through dynamically stable late case C mass transfer or common envelope ejection.